datetime review part 2 [Update 4]

[bearophile]

Steven Schveighoffer:

> Well, I'm not certain that this is the reason, but calendars are riddled  
> with corner cases.  I would expect a well-tested date/time library to test  
> all those corner cases.

I have never suggested to remove unit tests. But in several languages and projects there is the convention of moving the tests in a separated place when they become very large. Currently the unittest support in D doesn't allow to do this this well. So I suggest to improve the way DMD manages unittests, to allow a handy and safe move of them in another module, when the programmer desires so (named unittests are probably a good starting point for this).

Bye,
bearophile